1. Technical Field
The present invention relates to a DC/DC power converter. More specifically, the invention relates to a highly efficient DC/DC power converter that can be driven in both directions.
2. Description of the Related Art
In general, the topology used for a bidirectional DC-DC power converter comes in two types: full-bridge converter and current-fed converter. Such converters have the disadvantage of the control integrated circuit (henceforth referred to as IC) being comparatively expensive, and the switching device, namely, metal-oxide semiconductor field effect transistor, (henceforth referred to as MOSFET) having a high level of voltage and current stress, and therefore decreasing the efficiency of the system.
FIG. 2 is a circuit diagram of a bidirectional DC-DC power converter using the full-bridge topology. The operation in forward direction comprises: a DC/DC converter unit 20; a control unit 22 configured to send the gate waveform to each switch and to control the gate waveform so as to maintain the power output; an output side L-C filter unit 24; and lastly, an output voltage detector circuit 26. The DC/DC converter unit 20 comprises: 4 MOSFETs (Sp1, Sp2, Sp3, Sp4); a step-up transformer; and another 4 MOSFETs (Ss1, Ss2, Ss3, Ss4) configured to act as rectifier switches and to compare the voltage detected at the output voltage detector circuit 26 with the standard voltage at the control unit 22, adjusting the gate width of the MOSFETs and maintaining the output voltage at a consistent level.
The control unit transmits energy to the step-up transformer by switching on or off in turns the first switches on the first switching device transformer (Sp1, Sp4) and the first switches on the second transformer (Ss1, Ss4), or the second switches on the first transformer (Sp2, Sp3) and the second switches on the second transformer (Ss2, Ss3). The stepped-up energy goes through the rectifier switches (Ss1, Ss4, Ss2, Ss3) and converts to direct current (DC), finally outputting through the LC filter 203 consisting of a coil (L) and a capacitor (C).
The conventional full-bridge converter has the problem of the control IC being comparatively expensive, due to having to output four gate waveforms, and the problem that, the larger the capacity of the converter, the greater the switching loss at the four points, and therefore, efficiency vastly decreases.